Table of Content

25 July 2020, Volume 48 Issue 7

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Energy, Power & Electrical Engineering

Analysis on Heat Generation in a Lithium-Ion Battery Under Constant Power Discharging



GAN Yunhua, TAN Meixian, LIANG Jialin, et al

2020, 48(7):  1-8.  doi:10.12141/j.issn.1000-565X.190708

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Constant power discharging is a typical discharging mode of battery in the actual operating． The heat generated in the discharging process has a big influence on the performance and safe operation of battery． In order to study the heat generation characteristics of battery under constant power discharging，firstly，an electrochemical-thermal coupling model was established． Then，the rationality of the model was verified by experiments． Finally，the heat generation characteristics of the current collector，positive and negative electrodes，separator in a lithium-ion battery were studied． And the effects of discharging power and thickness of the positive electrode on the heat generation of each layer in the battery cell were discussed． The results show that，firstly，the heat generation rate of the negative electrode exhibits the highest degree of variation; secondly，the discharging power has little effect on the ratio of the heat generation of each layer to the total heat generation; thirdly，the heat generation ratio of the positive electrode is the largest (the ratios are all above 70% under different discharging powers); finally，the thickness increase of the positive electrode can reduce the heat generation of the battery，but this effect will de-crease as the thickness of the electrode increases．


Axial Thermal Circuit Model-Based Calculation of Contact Ｒesistance of Contact Surface Between the Overhead Ground Wire and Armor Rod



LIU Gang, GUO Deming, ZHENG Wencheng, et al

2020, 48(7):  9-19.  doi:10.12141/j.issn.1000-565X.190562

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As an important parameter for the electrical contact performance measurement，the size of contact re-sistance is directly related to the operation of electrical equipment． At present，the contact resistance is usually measured with the off-line experimental measurement method，but the measurement result often differs from the ac-tual operating state to a certain extent． So a method for calculation the contact resistance of contact surface based on the axial thermal circuit model was proposed． Firstly，an axial thermal circuit model was constructed taking the contact terminal of overhead ground wire and armor rod as the research object，and the thermal parameters of the model were obtained by genetic algorithm． Then，based on the calculation results of the GJ-50 overhead ground wire，the variation laws of thermal parameters of the model and contact resistance were discussed and analyzed．The results show that the AC contact resistance corresponding to different temperature during the transient tempera-ture rise of contact surface could be obtained accurately by using the proposed method． The contact resistance de-creases with the increase of load current under the steady state temperature，but it is not affected by the time calcu-lation step． The calculation method shows a high accuracy，and the maximum error between the experimental measurement results and the calculation results of contact resistance does not exceed 9%． In addition，the calcula-tion result is more accurate when the relationship between contact resistance and temperature is expressed by the formula proposed by Paulke et al．


A New Method for Calculating the Operation Times of Lightning Arresters with Fixed Clearance on Transmission Lines#br#



DENG Honglei TANG Chongwang LIU Gang et al

2020, 48(7):  20-27.  doi:10.12141/j.issn.1000-565X.190292

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The operation times of arrester counter is one of the main indexes for judging the operation status of ar-rester． It is very difficult to calculate the operation times of arrester through the artificial and unmanned aerial pho-tographs． So a new method was proposed to calculate the number of actions of arrester with fixed clearance based on the data of lightning location system，transmission line equipment account and lightning protection mechanism．The effectiveness of the method was verified by a practical example． Firstly，lightning-induced area of the line was determined by the parameters of transmission line and lightning current，and all lightning currents in lightning-in-duced area were calculated according to the installation time of lightning arresters and the data of lightning positio-ning system over the years． Then，the lightning resistance level of the line was calculated with method of regula-tions，and the maximum and minimum lightning current value and lightning shielding rate of the line were calculat-ed based on the improved electrical geometric model． Finally，the operation times of arrester with fixed clearance was calculated by analyzing the number of flashover caused by counterattack lightning and encircling lightning． The
case study shows that the operation times calculated by this new method are basically consistent with the actual op-eration times，and it can effectively calculate the probability of action times of arrester caused by counterattack lightning and encircling lightning．


Numerical Analysis of MILD Combustion of Organic Solid Waste Pyrolysis Gas



LIAO Yanfen, CHEN Shunkai, ZHANG Manyu, et al

2020, 48(7):  28-35,46.  doi:10.12141/j.issn.1000-565X.190883

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MILD combustion of pyrolysis gas is one of the key technologies for efficient conversion and utilization of organic solid waste．Compared with traditional single-component gas，solid waste pyrolysis gas has the characteris-tics of complex components，low heat value and poor combustion stability． In order to improve the efficient and clean utilization of solid waste pyrolysis gas，the effects of different fuels，air excess coefficients and air inlet cross-sectional areas on the combustion characteristics of solid waste pyrolysis gas and its MILD combustion formation conditions were studied with numerical simulation methods． The research results show that，compared with the sin-gle components of methane，the combustion process of the solid waste pyrolysis gas is sped up because of its high hydrogen content． In addition，its peak temperature is high，and its temperature field is unevenly distributed．Changing the air distribution conditions at the inlet of the combustion chamber has a significant impact on the com-
bustion process． With the reduction of excess air coefficient，the peak temperature in the combustion chamber de-creases，the overall temperature level rises，and the temperature distribution becomes more uniform，but at the same time the range of the high temperature region also increases significantly，resulting in an increase in NO con-tent at the outlet． Under the condition of low excess air coefficient，the reduction of the air inlet cross-sectional ar-ea can reduce the peak temperature in the combustion chamber，and the uniformity of temperature distribution can be effectively improved． In order to achieve MILD combustion of solid waste pyrolysis，the content of NO at the outlet should be reduced to no more than 0. 003%．


Distributed Calculation of Security-Constrained Optimal Energy Flow in Integrated Power and Gas Energy Systems



LIN Shunjiang, TANG Zhiqiang, XIE Yuquan, et al

2020, 48(7):  36-46.  doi:10.12141/j.issn.1000-565X.190225

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A security-constrained optimal energy flow calculation model for integrated power and gas energy sys-tems (IPGES) was established，considering the coupling of gas generators and motor driven compressors between power system and natural gas system． The model takes the total operating cost of the IPGES，that is，the sum of the cost of coal consumption by coal-fired generating units and the cost of natural gas consumption by gas sources of natural gas networks，as the objective function，and the security constraints of multiple N-1 contingencies in power systems and natural gas systems were considered． Firstly，the objective function of the original optimization model was divided by considering the influence of the transaction between the power network and the natural gas network．And the coupling equations of the gas generators and the motor-driven compressors were linearized by the first-order Taylor series expansion，respectively． Thus makes it possible to use the synchronous alternating direction multipli-er method (ADMM) for distributed solution of security-constrained optimal energy flow calculation model． Then the CONOPT solver in GAMS software was used to solve the optimal energy flow of power system and natural gas
system，respectively． Finally，the modified IEEE-39 bus power system and Belgium 20-bus natural gas system were taken as an example to validate the proposed model and solution algorithm． The results show that the proposed model and algorithm are correct and effective．


Evaluation on the Comprehensive Energy Efficiency of Power GridEnterprise Material Quality Control System Based on Combination#br# Weighting and Fuzzy Comprehensive Evaluation Method



DAI Zhou, WANG Gang, YAN Yingjie, et al

2020, 48(7):  47-54.  doi:10.12141/j.issn.1000-565X.190681

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Power grid enterprise material quality control is the most important step before the equipment being put into operation． It involves technology，management，and implementation，etc． Aiming at the problems of high com-plexity and difficult evaluation of the existing quality control system，an energy efficiency evaluation method based on combination weighting and fuzzy comprehensive evaluation was proposed，and it was validated by the data obtained from the 5 wholly-owned subsidiaries of Southern Power Grid in eastern and western China． Firstly，the various aspects of the quality control system was surveyed and a hierarchical index system of comprehensive energy efficiency evaluation was constructed． Secondly，subjective experience was combined with actual data by the fuzzy analytic hierarchy process (FAHP) and entropy weight method to obtain the dynamic combination weights，which ensures objectivity and accuracy． Finally，the overall energy efficiency was evaluated through fuzzy comprehensive evaluation method． The numerical example shows that the algorithm results are in line with objective facts，so the efficiency of the model is verified．


Traffic & Transportation Engineering

Urban Vehicle Trip Chain Ｒeconstruction Based on Gradient Boosting Decision Tree



XU Jianmin, WEI Xin, LIN Yongjie, et al

2020, 48(7):  55-64.  doi:10.12141/j.issn.1000-565X.190428

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A reconstruction method for urban vehicle trip chain based on gradient boosting decision tree was pro-posed to extract actual vehicle trajectories for transportation planning，traffic design，management and evaluation．Firstly，vehicles were matched by license plate number (LPN)，and the corresponding travel chains sorted by time stamp were initially extracted and split according to the intersection adjacency matrix and estimated link travel time． Subsequently，the key features that affecting vehicle route choice were identified based on travel behavior a-nalysis and traffic conditions，and a reconstruction method for local lost trip chain was developed based on gradient boosting decision tree (GBDT)． Finally，taking the field LPN data from Nanming district of a Chinese city as an example，the accuracy and calculation efficiency of the proposed method and existing ones were verified． The re-sult shows that the proposed method can achieve a high reconstruction accuracy of 91%，and it superior to the tra-ditional ones in urban vehicle trip chain reconstruction．


Intelligent Vehicle Obstacle Avoidance Trajectory Planning in Structured Road Based on Analytic Hierarchy Process



ZENG Dequan, YU Zhuoping, XIONG Lu, et al

2020, 48(7):  65-75.  doi:10.12141/j.issn.1000-565X.190568

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The optimal trajectory selection system based on analytic hierarchy process (AHP) was designed，in order to plan optimal obstacle avoidance trajectory for intelligent vehicle in structured road． Firstly，cubic B-spline curve was employed as the planner to generate path with continuous curvature and controlled maximum curvature，based on which path sets were constructed．Secondly，in order to achieve quantitative expression of subjective and objective indicators，the AHP system for optimal path selection was constructed and the optimal path was selected，by considering smoothness and economic criteria as the criteria，path length，curvature sum，curvature change rate sum and distance from target point as sub-criteria． Then，cubic polynomial was used to represent the change of velocity relative to time，so as to satisfy the continuity of velocity，acceleration and acceleration derivative． Fi-nally，test scenarios were designed according to national standards to verify the stability of the method and the real- time performance of the algorithm． After 5 000 cycles of simulation test，the result shows that the algorithm has a good real-time performance． The probability of feasible trajectory planning within 0. 1 s is 94%，while within 0. 16 s it is 100%． The planned trajectory is convenient for vehicle tracking and the method has a high stability． The peak lateral error of real vehicle test is less than 0. 21 m，the peak speed error is less than 0. 42 m/s，and the av-erage speed error is less than 0. 11 m/s，which show an overall trend of convergence．


Characteristics of Vehicle Spatiotemporal Diagram Under the Emergency Braking Warning



LI Haijian, ZHAO Guoqiang, YANG Yanfang, et al

2020, 48(7):  76-84.  doi:10.12141/j.issn.1000-565X.190889

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Emergency braking event of the vehicle in front is one of the main causes of a forward collision． If the driver can sense the emergency braking event of the vehicle in front timely，the coping behavior can be changed from passive visual stimulation to active coping behavior based on psychological expectation，which will greatly re-duce the accident rate． Based on driving simulation technology，an emergency braking event in the cooperative ve-hicle infrastructure system was designed to provide the emergency braking warning information of the vehicle in front with the vehicle-mounted Human Machine Interface (HMI) at the distance of 360 m and 290 m． Driving behavior data and evaluation indexes were obtained from driving behaviors of qualified drivers in the driving simulation experi-ment． After a comparative analysis of driving behavior data with and without HMI warning information，a method was proposed for analyzing the driving characteristics of the emergency braking event of the vehicle in front in the cooperative vehicle infrastructure system based on spatiotemporal diagram． The driving confidence characteristics of
35 drivers in emergency braking event were analyzed based on their average acceleration characteristics． The re-sults show that when the HMI warning information is available，the drivers tend to decelerate earlier with lower speed control intensity than that when the HMI warning information is not available． According to the curvature in-dex，the speed control intensity is reduced by 39. 4%． When the HMI warning information is available，the speed control is more leisurely，and the drivers can proactively respond to the risk environment with the characteristics of driving confidence．


Impact of Shared Bicycles on the Configuration of Travel Mode in Commuting Corridor



YAO Enjian, LI Cuiping, HUAN Ning, et al

2020, 48(7):  85-92,142.  doi:10.12141/j.issn.1000-565X.190606

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In order to deeply analyze the impact of the appearance of shared bicycle on the travel structure of com-muter corridor，the commuting mode choice behavior was interpreted as a joint selection behavior for the main tra-vel modes and the connection modes，and a two-layer NL (Nested Logit) model was constructed to describe the hi-erarchical decision-making process of commuters． On this basis，actual cases under different commuting distances were selected． The sharing rates of the main travel modes and transfer modes of public transportation before and af-ter the introduction of shared bicycles were calculated． The results show that the sharing rate of shared bicycles reaches 13. 2% in short distance commuting，which has a significant substitution effect on ground buses and pri-vate bicycles but has less impact on the sharing rate of the subway． In medium and long distance commuting，the shared bicycle is more likely to be used as a connection way of the subway，and it increases the sharing rate of the subway by 3. 6% and causes a decline in the sharing rate of ground buses，private cars and taxis． In general，the shared bicycle can facilitate the connection of traditional public transportation modes and reduce the pressure of pas-
sengers from short-distance travel during the morning peak． In addition，the shared bicycle can increase the attrac-tiveness of the subway in long-distance travel and reduce the travel of cars and taxis to a certain extent．


Shear Lag Effect of Corrugated Steel-Concrete Composite Multi-Box Cable-Stayed Bridge



ZHAO Hu GOU Hongye NI Yingsheng

2020, 48(7):  93-103.  doi:10.12141/j.issn.1000-565X.190669

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Many multi-box corrugated steel web low tower cable-stayed bridges have been built across the world，but single-box multi-chamber low tower cable-stayed bridges with corrugated steel and concrete composite webs are still rare． The shear lag effects of this new combined box profile sections need to be further explored． At present，the commonly used analytical methods for designing the analysis of shear lag effect mostly adopt plane beam model，single beam model，solid model，etc． But these calculation models lack refinement when analyzing various stress indexes of shear lag effect． The spatial grid analysis model can make up for the shortcomings of these analysis methods． Therefore，the spatial grid analysis method was adopted to discuss the shear lag effect of low tower cable-stayed bridges with low towers in this paper． Firstly，the principle of shear lag effect，the method of spatial grid a-nalysis and the feasibility of the method verifying the space grid analysis of corrugated steel webs were analyzed in detail． Then a single-box multi-chamber low tower cable-stayed bridge with corrugated steel and concrete composite
webs was taken as a typical case，and its shear lag effect was analyzed by a spatial grid model． The results show that，firstly，the top slab of this type of box girder shows obvious positive shear lag，and the bottom slab shows small positive shear lag; secondly，the effect of positive shear lag at the concrete web is significantly greater than that at the corrugated steel web; thirdly，the shear lag coefficients show a certain change law． Through case analysis，the distribution law of shear lag coefficients in key sections of this type of steel-concrete composite struc-ture along the horizontal and vertical directions was obtained，which can provide a reference for similar projects．At the same time，the validity and accuracy of the spatial grid analysis method is verified． The spatial grid analysis model makes up for the shortcomings of conventional analysis methods and brings new ideas and directions for the refined design of bridges．


Calculation of Load Transverse Distribution Coefficient of Multi-Beam Improved Composite Small Box Girder Bridge with Corrugated Steel Webs Considering Shear Deformation



MA Chi LIU Shizhong

2020, 48(7):  104-114.  doi:10.12141/j.issn.1000-565X.190885

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At present，there is little research on the influence of shear deformation on the transverse load distribu-tion of steel-concrete composite box girder bridge． Firstly，on the basis of considering its own shear deformation，the stiffness reduction coefficient was obtained by sinusoidal load． The eccentric pressure method，the modified eccentric pressure method and the rigid connection beam method considering the shear deformation effect were used to deduce the calculation formula that calculates the transverse load distribution coefficient of the composite small box girder bridge of multi beam type corrugated steel webs-steel floor-concrete roof (CSWSB)． Then，a real bridge with multi beam type improved corrugated steel webs composite small box girder was selected for experimen-tal study． Finally，the results calculated by the calculation methods discussed in this paper were compared with the results of the finite element method and the test values． The results show that the deflection value of the rigid connection beam method considering the shear deformation effect is closer to the simulation value of ANSYS，and
the rigid connection beam method considering the shear deformation effect should be used to calculate the transverse load distribution coefficient of the midspan． When the bridge structure does not meet the narrow bridge conditions，the rigid connection beam method considering the shear deformation effect should be used to calculate the transverse load distribution coefficient of the midspan section． When the bridge structure meets the narrow bridge conditions，the modified eccentric pressure method considering the shear deformation effect can be used to calculate the trans-verse distribution coefficient．


Architecture & Civil Engineering

Artificial Neural Network Prediction Model for Compressive Strength of Compacted Earth Blocks



WANG Yihong, ZHANG Jianxiong, LAN Guanqi, et al

2020, 48(7):  115-121.  doi:10.12141/j.issn.1000-565X.190861

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A BP neural network model and a radial basis (ＲBF) neural network model were set up respectively to predict the compressive strength of compacted earth blocks． The prediction model for the compressive strength of compacted earth blocks was based on 91 groups of experimental research data collected under the action of multiple factors by domestic and foreign scholars，and the influence of compaction pressure，moisture content，cement con-tent and height-thickness ratio on the compressive strength of compacted earth block was considered． The neural network predicted results were compared with the predicted results of regression analysis model and the experimental values． The results show that the prediction accuracy of artificial neural network model is better than that of regres-sion analysis model． And there is a complex nonlinear relationship that the regression analysis model cannot handle between the compressive strength of the compacted earth block and its mixture ratio，compaction pressure and height-to-thickness ratio． The overall prediction effect of BP neural network model is good，but it is easy to fall in-to local optimum． ＲBF neural network model can reliably predict the compressive strength of compacted earth blocks． The mean value of the ratio between the predicted results and the experimental values is 1. 007，with a standard deviation of 0. 085． The prediction model has a high accuracy and can effectively solve the complex non-linear relationship between compressive strength and its influencing factors，and it can provide reference for the de-sign of mix proportion for compacted earth blocks．


Experimental Study and Model Calculation on Crack Development of Polypropylene Fiber Ｒeinforced Concrete Beams



LI Fuhai, GAO Hao, WANG Jiangshan, et al

2020, 48(7):  122-133.  doi:10.12141/j.issn.1000-565X.190926

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Eight PP-ECC beams and two RC beams were fabricated in order to investigate the crack development law of PP-ECC beams under bending load． Firstly，the crack development pattern，crack width and crack exten-sion height of PP-ECC beams were studied by four-point bending load，and compared with those of RC beams．Then the average crack spacing model，the maximum crack width model and the maximum crack extension height model were established based on the bond-slip theory and plane cross-section assumptions，considering the tensile capacity of the ECC beam when the beam was flexed． And the rationality and accuracy of each model were verified by comparing the model calculation results with the test results． The results show that PP-ECC has obvious strain-hardening characteristics under uniaxial tension，showing a mode of multiple micro-cracks development． The num-ber of cracks in PP-ECC beams under bending load is significantly more than that in ＲC beams，and cracks develop through the whole test process． The width and extension height of main cracks in PP-ECC beams are smaller than
that in RC beams，and cracks show more uniformity with the increase of load． The accuracy coefficient of PP-ECC beam average crack spacing model based on bond-slip theory is between 0. 95 and 1. 05，the accuracy coefficient of the maximum crack width model is between 0. 85 and 1. 2，and the accuracy coefficient of the maximum crack extension height model established based on plane cross-section assumption is between 0. 95 and 1. 1．


Sound Absorption Coefficient Measurement Based on Three-Dimensional Sound Intensity Method



WANG Hongwei GAO Yifan YU Xiu

2020, 48(7):  134-142.  doi:10.12141/j.issn.1000-565X.200018

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Reverberation chamber method and the standing wave tube method are two main traditional methods to measure the sound absorption coefficient． But they are easy to be limited by experimental conditions and have some limitations in practical engineering applications． Based on the vector characteristics of the measured three-dimen-sional sound intensity，a four-microphone was used to calculate the corresponding sound absorption coefficient by measuring the amplitude of the sound intensity reflected by the tested specimen and the total reflector plate，re-spectively． This method can not only measure the absorption coefficient of materials，but also measure the inci-dence angle and reflection angle of sound waves． Firstly，the principle analysis of the measurement of the sound absorption coefficient was carried out by the three-dimensional sound intensity method． Then the software was used to simulate the system，and the measurement errors of the absorption coefficient in different frequency band，diffe-rent absorption coefficient and different incidence angle were discussed． At last，the method was used to measure the three materials，and the results were compared with the results of standing wave tube method，and the directivi-ty error was tested． The results show that the error range of the absorption coefficients of 630 ～ 4 000Hz measured
by this method and the standing wave tube method is ± 0. 02 ～ ±0. 10，the directivity error is between 1 ° and 6 °，and the directivity error of different incident angles from 0 ° to 80 ° is between 1 ° and 3. 5 °．


Research on Natural Vibration Characteristics of Coupling Hangers Considering Bending Stiffness



CHEN Wei, WANG Ronghui, ZHOU Haoen, et al

2020, 48(7):  143-154.  doi:10.12141/j.issn.1000-565X.190857

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After setting the anti-vibration mount，the natural vibration characteristics of the suspension bridge sus-pender is different from that of the single cable． The vibration of the suspension bridge suspender is a comprehen-sive reflection of the interaction of the cable strands at the same lifting point． In order to study the natural vibration characteristics of suspender with the anti-vibration mount，the model of double strands coupled system considering bending stiffness of the strand was proposed． Firstly，the theoretical formula of the coupled vibration of the system was derived． Then the natural frequency was solved and verified by experiments and numerical examples． Finally，the influence of the bending stiffness of the suspender，the coupling position，the coupling stiffness of the anti-vi-bration mount，and the length of the suspender on the natural vibration characteristics of suspender was studied by taking the typical suspender of the Aizhai Bridge as the engineering background． The results show that the natural frequency of the suspender with the anti-vibration mount is obviously increased after considering the bending rigidity
of the suspender． And the shorter the cable，the bigger the increament． The anti-vibration mount ensures the con-sistency of the in-phase global modes of the two main strands． There are local modes of single strand (come in pairs when the anti-vibration mount is located at 1/2 of the strand) and out-of-phase modes between the in-phase global modes． The position of the anti-vibration mount has a significant influence on the natural vibration frequency and the mode shape of the out-of-phase modes． Compared with the rigid anti-vibration mount，the flexible anti-vi-bration mount causes decrease of the natural vibration frequency value of the out-of-phase modes． The smaller the rigidity，the greater the difference． For different lengths of suspenders，the anti-vibration mount can be regarded as a rigid anti-vibration mount when the rigidity is set to be k≥5 ×10⁶ N/m．